Press-fitting apparatus



June 29, 1965 P, ASHURKOFF PRESS-FITTING APPARATUS 2 Sheets-Sheet '1Filed June 21, 1963 INVENTOR.

I BY l sr fiskmiaf P. ASHURKOFF PRESS-FITTING APPARATUS June 29, 1965 2Sheets-Sheet 2 Filed June 21, 1963 mvmwon BY ezer .i /hrkoff A T TOE/YEY United States Patent 3,191,279 PRESS-FITTING APPARATUS PeterAshurlkofi, Grosse Pointe Farms, Mich, assignor to General MotorsCorporation, Detroit, Mich, 211 corporation of Delaware Filed June 21,1963, Ser. No. 289,644

8 Claims. (Ci. 29-200) This invention concerns an apparatus thatutilizes vibratory energy for facilitating the joining of two membershaving an interference fit.

The use of vibratory energy for press-fitting two members together isnot new and one example of an apparatus of this sort can be seen inco-pending patent application Serial No. 225,036, de Wilde filed Sept.20, 1962, and assigned to the assignee of this invention. The apparatusshown in the de Wilde application includes a fiexural member in the formof a disc which is vibrated while a load is applied to the apparatus inthe direction of insertion. The disc is connected to one of two membersbeing press-titted and supplies vibratory energy thereto for jointingthe members. Some advantages of this apparatus are that it decreases thetime for external load necessary for mating the two members andeliminates galling frequently occasioned by the erratic movement of theinserting member during a conventional press-fitting operation.

The present invention contemplates an improved vibratory apparatus ofthe above-described type that comprises a flexural bar means coupled tovibration generating means in a manner that permits the latter toprovide a resonant standing-wave movement of the bar. Means connect ananti-nodal point of the bar with one of the members to be joined so thatthe movement at this point is transmitted to that member during thepress-fitting opera-ti-on. In the preferred form, the flexural bar meansconsists of two elongated cylindrical members co-axially fixed to eachother in a manner whereby the vibration generating means and theabove-mentioned anti-nodal point are located side-by-side. In addition,spring means in the form of elastic bolts are used for connecting theanti-nodal points with the member being inserted so that aunidirectional force is applied by the vibratory apparatus foraccomplishing the press fit.

,A more complete understanding of the invention can be derived from thefollowing description taken in conjunction with the drawings, in which:

FIGURE 1 is an elevation view showing a vibratory apparatus made inaccordance with the invention and being used for inserting a cylinderliner into an engine block,

FIGURE 2 is an enlarged view taken on line 22 of FIGURE 1, I FIGURE 3 isan enlarged view of the vibration gen,- era-t-ing means taken on lines3-3 of FIGURE 2, and

FIGURE 4 is a view taken on lines 4-4 of FIG- URE 3.

Referring now to FIGURE 1 of the drawings, for illustrative purposes apreferred embodiment of the vibratory apparatus made in accordance withthe invention, and generally indicated by the numeral 10, is shown beingutilized for press-fitting a cylindrical liner 12 into a cylinderopening 14 of a block 16. The block is rigidly held in position throughsuitable hold-down clamps 18 and 20 which maintain the opening 14 in avertical position for receiving the liner. In the preferred form, thevibratory apparatus is of the hand-operated type and, accordingly,includes a handle portion 22 which permits the operator to grasp andmanipulate the apparatus during a press-fitting operation.

More specifically, the vibratory apparatus comprises 'a pair of coaxialflexu-ral bar members 24 and 26, the latter of which supports thevibration generating means general-1y indicated by the numeral 28. Bothbars are made in a tubular form with the inner passage 30 in bar 26serving to connect the vibration generating means 28 with a source 3-2of pressurized air. A valve 34, located in an air line 36 that connectsthe air source with the vibratory apparatus, serves to control theamount of air being supplied to the vibration generating means whichwill be described in more detail hereinafter. The bar member 24, as seenin FIGS. 1 and 2, is of a greater diameter than bar member 26 and hasthe inner portion thereof suitably bored for concentricallyaccommodating the latter member. In this connection it can be seen thatthe upper portion of bar member 26 protrudes through an opening 38 inbar member 24 and terminates with suitable threads which accommodate anut 40. A tubular spacer 42 is provided between the nut 40 and barmember 24 so that upon tightening the not a shouldered portion 44 of barmember 26 is sea-ted in a counterbore 46. Thus, the two bar members arerigidly connected to each other and the handle portion 22 is formed.

The lower end of bar member 24 has a portion 48 of a reduced diameterthat can be piloted onto one of the two members being joined, which inthis instance would be the liner 12. In addition, as best seen in FIGS.2 and 4, a pair of opposed crescent-shaped flanges 50 are integrallyformed adjacent the portion 48 and serve to threadably accommodate oneend of a pair of bolts or spring members 52. The opposite end of eachbolt includes a nut 54 that together with a cap 56 secures the liner tothe vibratory apparatus.

As viewed in FIG. 3, the vibration generating means 28 comprises a pairof identical air-driven vibrators, each of which includes a roller-typemass 58 housed within an annular working chamber defined by acylindrical member 60. A plurality of tangentially directed passages 62are formed in the member 60 to serve as nozzles for directing a highvelocity air stream against the periphery of the mass 58 and therebycause it to orbit about the Working chamber. The vibrators are laterallyspaced firom each other and adapted to have the associated masses drivenin opposite directions so as to develop counter-rotating force vectorsso that all forces other than those acting in a vertical direction arecancelled. Thus, the effective force acting on the lower end of the barmember 26 is a reciprocating force along the longitudinal axis of thelatter at the operating frequency of the vibrators. In this connection,it should be noted that each of the vibrators is made according to theprinciples stated in the patent to Svenson 2,194,410 and, accordingly,enjoys a frequency step-up which gives a number of force impulsesgreater than one for each complete revolution of the mass 58 about itsaxis. As a result, although these vibrators are of a mechanical type,they are able to operate at frequencies much higher than normallyattributed to vibrators other than the electrically-driven type.

In assembling or joining two members having an interference fit such .asthe illustrated liner and block, the member being inserted wouldinitially be connected to the vibratory apparatus. In this instance,this would be accomplished simply by placing one end of the liner overthe reduced diameter portion 48 while piloting the cap member 56 ontothe outer ends of the bolts 52. Thereafter the liner would be securelyattached to the apparatus by means of the nuts 54. The operator wouldthen position the lead end of the liner into the block opening 14 so asto have the longitudinal axis of the apparatus in alignment with that ofthe accommodating bore as shown in FIG. 1. Valve 34 would then be openedto direct pressurized air to the vibration generating means 28 so as todrive the vibrators in a counter-rotating manner and thereby develop areciprocating force, as described above,

which serves to elastically elongate and contract the lower end of barmember 26. This'reciprooating force sets up longitudinal waves which aretransmitted through the rigid connection between the barmembers to theportion 48 or the lower end of the bar member 24 so that the latter alsoexperiences an elastic elongation and contraction. V I a Inasmuch as-theportion. 48 is connected with the liner, this'movement, augmented with asmall amount of pressure exerted by the operator in the direction ofinsertion, serves to readily insert the liner into the opening 14 p Formost efficient operation it has been found that the vibration generatingmeans should be operated in the I the use of the elasticbolts and wouldcall for the operator to manually position the liner into the'bore afterwhich time the vibratory apparatus would be placed on the liner. Uponenergization of the vibrators and with the help of a downward forcebeing applied onto the vibratory apparatus in thedirection of insertion,the liner will be insertedin the opening, however, a noticeablehammering resonant frequency range of the flexural barmembers.

Moreover, it'hasbeen found that optimum results are obtained when bothbar members are designed so as to'have equal linear momentum. In thisregard'and with refer- 'ence to the particular embodiment of FIGURE 1,both the inner and outer flexural bar members 24 and 26 were made asquarter-Wave-length bars with the point of coneffect will occur betweenthe apparatus and the liner; Moreover, the amount of added forcenecessary to accomplish insertion in this form of the apparatus would bemuch greater than when the liner is connected to the latter by theafore-described spring means. b

Although only one vembodiment of this invention has been shown, otherforms will be apparent to those skilled in the art of vibratory devices.Therefore, the inventor does not wish to be limited except bythe scopeof the appended claims. w

nection between'the two constituting a'nodal point, while the free endsof both bars are anti-nodal points. Thus, the bars together constitute ahalf-wave-length bar which has, been, in effect, cut in half with theinner ends thereof interconnected so as to place the outer ends adjacentto each other, In this instance, this has been accomplished by insertingone of the bars within the other. As is. well known to those skilled inthe science of acoustics, a half wave-length bar vibrated at a frequencyequal to or in the range of the resonant frequency of the bar and in alongitudinal standing wave mode has the opposite ends thereof moving indirections 180 out of phase, with the center thereof being a point ofminimum movement designated as the nodal point, while the outer ends.are anti-nodal points or points of maximumv movement.

Thus, as explained above, when the vlbrators are operated at or in therange of the resonant frequency of the bar members, the portion 48elongates and contracts at this frequency. Because of the manner theliner is connectedv with the vibratory apparatus, any inserting'movementcaused by the-elongationofthe flexural member. 24 would beoffset bythecontracting movement'thereof and therefore no appreciable insertioncould be realized. This, however, is not the case since the bolts byhaving the intermediate portions thereof of a reduced diameter, act assprings so that the contracting movement ofthe portion 48 causes a'slight'elongationof the bolts without removing thel-iner. In order toachieve this result, the spring constant of the bolt is relatedto thefrictional forcesretaining the liner in the bore. In other words, thefrictional force must be greater than the force necessary to cause anelastic stretching of the bolt with? out exceeding the-elastic limit ofthe latter. a It should be apparent from the above that the use of theelasticbolts is one of the significant features of this,

invention. This is so because, as a practical matter, by providing aspring type connection between the anti-node point of the flexuralapparatus utilizes the down stroke for striking the .liner and pushingit into the block, however, on the upstroke the bolt stretches as aspring permitting the apparatus to it would appear that prising anelongated bar means, vibration generating means coupled to one end ofsaid bar means so as to 1 cause a resonant standing-wave movement of thelatter in a. longitudinal mode to permit the other end of said bar meansto reciprocate in a longitudinaldirection, and means on said other endfor engaging one of said two members and thereby transmitting vibratoryenergy thereto for joiningsaid members together.

2. An apparatus for facilitating the press-fitting of two memberstogether where oneof the members has an opening and the other is to beinserted; into the opening, comprising a bar, vibration generatingmeans. coupled to said '1 bar to cause a standing-wave movement of thelatter with nodal and antinodal points along the length of the bar, andelastic means for supporting one .of. said two meme bersrat an antinodalpoint of said bar. whereby the bar movement at this point is transformedto aunidi'rectional bar member 24 and the liner 12, the

momentarily leave theliner without withdrawing the late ter from theblock. Hence, the alternate elongation and contraction at the anti-nodalpoint of the vibratory apparatus is rectified so that the net effect onthe liner is a unidirectional force for inserting the liner.

Finally, it should be noted that during a press-fitting operatiomthe useof an elastic connection between the vibratory apparatus and the memberbeing inserted-is not absolutely necessary. In other words, as seeninxFIG. l, the bolt and cap member could be removed and the apparatusplaced on the liner, as shown in FIG. 1, ln'this instance, however theoperating procedure would beslightly 7 different than-that explainedearlier in connection with force for joining said two members.

3. An apparatus for facilitating the press-fitting of two memberstogether where one of the membershas'an opening an'd'the other is to beinserted into the opening, comprising an elongated bar means, vibrationgenerating means coupled to one end of saidbar means so as to cause astanding-wave movement of the latter in a longitudinal mode to permitthe other end of said bar means to rec procate in a longitudinaldirection, and elastic means for supportingone of said two members atsaid other end of said her means whereby the reciprocating movement ofsaid other .end is transformed to a unidirectional force for joiningsaidtwo members.

' 4. An 1 apparatus for joining two members with an interference fitcomprising first and second elastic bars havingthelsame linear momentum,said bars being fixed to each other along alongitudinalaxis, vibrationgenerating means fixed to one of said bars at one end thereof. andadapted to vibrate said bars in a longitudinalmode with a standing-wavewhereby the point of connection between said bars is a nodal point whilethe free end of the other of said, bars is an antinodal point, and meanslocated at said free end of the other of said bars for engagement withone, of said two members for transmitting vibratory energyto the. latterto facilitate the joining operation of said two members.

5. An apparatus for joining two members with an interference fitcomprising a first and second bar having the same linearmomentum, saidbars being fixed to each other along a longitudinal axis, a pair offluid-driven vibrators fixed to one of said bars at one end thereof andadapted to vibrate said bars in a longitudinal mode with a standing-wavewherebythe point of connection between said bars is a nodal point whilethe free end of the'other of said bars is an antinodal point, and meanslocated at said free end of the other of said bars for engagement withone of saidtwo members for transmitting vibratory energy to 5 the latterto facilitate the joining operation of said two members.

6. An apparatus for joining two members with an interference fitcomprising first and second elongated bars having the same linearmomentum, said first bar having an elongated opening formed thereinalong its longitudinal axis, the second bar located in said opening andconnected at one end to the first bar, vibration generating means fixedto the second bar at the free end thereof and adapted to vibrate saidbars in a longitudinal mode with a standing-wave whereby the point ofconnection between said bars is a nodal point while the free end of thefirst bar is an antinodal point, and means located at said free end ofthe first bar for engagement with one of said two members fortransmitting vibratory energy to the latter to facilitate the joiningoperation of said two members.

7. An apparatus for joining two members with an interference fitcomprising an elongated cylindrical first bar having a longitudinalpassage for compressed air formed therein, a pair of air-drivencounter-rotating vibrators connected to one end of said bar andcommunicating with said passage, a sleeve-shaped second bar ofsubstantially the same linear momentum as said first bar, said first barbeing located within said second bar and being fixed to one end of thelatter, the other end of said second bar being provided with elasticmeans for supporting one of said two members during the joiningoperation, and a source of compressed air for driving said vibrators atthe resonant frequency of the bars whereby the latter vibrates with astanding-wave in a longitudinal mode.

8. The apparatus of claim 6 wherein each of said vibrators comprises aroller adapted to be driven in an orbital manner so as to generate arotating force vector in a plane parallel to the longitudinal axis ofsaid first and second bars.

References Cited by the Examiner UNITED STATES PATENTS 2,194,410 3/40Svenson 259-1 2,561,577 7/51 Knudsen 173-132 WHITMORE A. WILTZ, PrimaryExaminer. THOMAS H. EAGER, Examiner.

1. AN APPARATUS FOR FACILITATING THE PRESS-FITTING OF TWO MEMBERSTOGETHER WHERE ON OF THE MEMBERS HAS AN OPENING AND THE OTHER IS TO BEINSERTED INTO THE OPENING, COMPRISING AN ELONGATED BAR MEANS, VIBRATIONGENERATING MEANS COUPLED TO ONE END OF SAID BAR MEANS SO AS TO CAUSE ARESONANT STANDING-WAVE MOVEMENT OF THE LATTER IN A LONGITUDINAL MODE TOPERMIT THE OTHER END OF SAID